With the development of the power electronics technology, high-frequency isolated power conversion is more and more applied to the power grid, becoming an important means to realize fast and flexible control in the power grid. However, the wide application of power electronic devices in AC/DC applications leads to an increase in the harmonic content of the grid current and seriously threatens the normal operation of the power grid. In order to reduce the harmonic pollution caused by power electronic devices and improve the power quality of the power grid, the International Electrotechnical Commission has issued and revised the harmonic standards such as IEC61000-3-2 and IEC555-2, and made uniform and clear regulations on the harmonic standards that various types of electrical equipment need to meet. Power Factor Correction (PFC) may reduce input current distortion of electrical equipments, improve input power factor, and reduce the harmonic pollution of converters to the power grid. It has become a necessary technical means for various electrical equipments to meet relevant harmonic standards. The AC/DC converter using PFC technology is called a PFC converter, which may realize the sinusoidal control of the input current waveform and make the phase of the input current waveform the same as the phase of the input voltage, and has excellent suppression effect on the input harmonic current, thus obtaining a wide range of applications and concerns.
The AC/DC converter may be classified into an isolated type and a non-isolated type depending on whether or not a transformer is used for isolation in the converter. In many applications, isolated AC/DC converters are required for safety and for the match of input voltages with output voltages. The Isolated AC/DC converter may be classified into single-stage and two-stage depending on the form of power change. The single-stage isolated AC/DC converter omits the first stage converter and directly performs energy conversion, which reduces the complexity of the circuit and improves the system efficiency.
The Dual Active Bridge-Isolated Bidirectional DC/DC Converter (hereinafter referred to as a DAB converter) based on phase shift modulation scheme (PSMS) has advantages of high power density, fast dynamic response, easy realization of soft switching, electrical isolation of primary and secondary sides, bidirectional flow of power, and the like, and is popular in applications such as uninterruptible power supply, electric vehicles, solid state transformers, and the like. The DAB-based single-stage isolated PFC converter achieves the purpose of improving power factor and reducing harmonic distortion by reasonably controlling the DAB converter to make its input current sinusoidal. Usually, it is necessary to add an inner current loop controller to control the input current. However, the inner current loop reduces the bandwidth of the system and increases the difficulty of the control system design. Therefore, how to properly control the DAB converter to make the input current sinusoidal, so as to achieve direct control of the input current, becomes a major challenge for the new generation of isolated PFC converters in the field of high frequency and high power density.